HEAT CONDUCTIVITY OF THE SOIL 



459 



sloped away from the sun would also receive the sun's 

 rays for a shorter period of each day. Wollny found 

 in Germany that the temperature of a sandy soil at 

 six inches depth on a south slope of 30 averaged 3.1 

 Fahr. warmer than the corresponding slope to the 

 north. King found the following differences in tempera- 

 ture between the level and an 18 south slope, in Wis- 

 consin, in July. 



Table LXXII 



The north slope ordinarily has the most uniform 

 temperature. 



328. Conductivity. The conductivity of the soil 

 for heat depends upon four factors. These are: (1) Com- 

 position. (2) Texture. (3) Structure. (4) Moisture 

 content. The relative influence of these factors, as 

 reported by Warington from the results of Pott, are 

 shown in Table LXXIII on page 460. 



Quartz has the largest power to conduct heat of 

 any of the soil constituents studied. The effect of lime- 

 stone and quartz stone is probably a textural one, as 

 is shown by the fact that the coarser the texture the 

 greater the conductivity. A compact soil conducts 

 heat more readily than a loose one. But, while a com- 

 pact soil will receive heat most rapidly, it also gives 



